Aβ₁₋₄₀ Enhances Platelet Sensitivity to Thrombin via NADPH Oxidase-ROS Signaling and Integrin α_IIbβ_₃ Engagement

Alzheimer's disease (AD) is increasingly recognized as a disorder with significant vascular involvement, with microvascular damage and thromboinflammation often preceding classical amyloid pathology by several years. Elevated levels of prothrombin and thrombin, along with aberrant platelet activation, have been reported in individuals with AD. We hypothesized that platelet hyperactivity in AD results from an exaggerated response to thrombin in the presence of elevated amyloid beta 1-40 (Aβ₁₋₄₀), a peptide that accumulates during the early stages of AD. Platelet activation in response to Aβ₁₋₄₀ and thrombin was assessed using aggregation assays with an aggregometer, adhesion measurements by confocal microscopy, and spreading via both confocal microscopy and scanning electron microscopy. Reactive oxygen species (ROS) production and integrin α_IIbβ₃ activation were quantified by flow cytometry. The roles of NADPH oxidase (NOX), ROS, and integrin signaling were examined using selective inhibitors. Aβ₁₋₄₀ significantly enhanced thrombin-induced platelet adhesion, aggregation, and spreading via NOX-derived ROS and integrin α_IIbβ₃ activation. Aβ₁₋₄₀ also promoted platelet binding to fibrinogen and cerebrovascular endothelial cells, accompanied by distinct morphological changes. Inhibition of NOX or integrin α_IIbβ₃ significantly reduced these effects. These findings identify a novel Aβ₁₋₄₀-NOX-ROS-integrin α_IIbβ₃ axis that drives platelet hyperactivation and cerebrovascular interactions in AD. Targeting this pathway with antithrombotic or antioxidative strategies may offer therapeutic potential in mitigating AD-associated vascular pathology.